Diagnostic systems and methods for engine knock sensors

Abstract

An engine control system includes a digital signal processing (DSP) module that generates a fast Fourier transform (FFT) of an engine knock signal generated by an engine knock sensor. An intensity determination module determines an engine knock intensity based on one of a maximum of and an average of the FFT. A status determination module determines a status of the engine knock sensor based on the engine knock intensity, a plurality of predetermined knock intensity thresholds, and a rotational speed of an engine crankshaft.

1. An engine control system comprising:
 a digital signal processing (DSP) module that generates a fast Fourier transform (FFT) of an engine knock signal generated by an engine knock sensor; 
 an intensity determination module that determines an engine knock intensity based on one of a maximum of and an average of the FFT; and 
 a status determination module that determines a status of the engine knock sensor based on the engine knock intensity, a plurality of predetermined knock intensity thresholds, and a rotational speed of an engine crankshaft. 
 
     
     
       2. The engine control system of  claim 1 , wherein the predetermined knock intensity thresholds are based on the rotational speed of the engine crankshaft. 
     
     
       3. The engine control system of  claim 2 , wherein the plurality of predetermined knock intensity thresholds includes a plurality of low intensity thresholds and a plurality of high intensity thresholds. 
     
     
       4. The engine control system of  claim 3 , wherein the status of the engine knock sensor is set to failure when the engine knock intensity is between one of the low intensity thresholds and one of the high intensity thresholds. 
     
     
       5. The engine control system of  claim 4 , wherein a failure count is incremented when the status of the engine knock sensor is set to failure during a predetermined time interval. 
     
     
       6. The engine control system of  claim 5 , wherein the failure count is output and reset to zero after the predetermined time interval. 
     
     
       7. The engine control system of  claim 6 , further comprising:
 a knock control module that actuates one or more of a plurality of fuel injectors and a plurality of spark plugs based on the engine knock signal when the failure count is less than or equal to a predetermined failure count threshold. 
 
     
     
       8. The engine control of  claim 1 , wherein the FFT includes a plurality of subsets corresponding to a plurality of frequency ranges. 
     
     
       9. The engine control system of  claim 8 , wherein each of the subsets includes a plurality of intensities corresponding to a plurality of frequencies. 
     
     
       10. The engine control system of  claim 9 , wherein the intensity determination module determines the engine knock intensity based on one of a maximum of and an average of intensities corresponding to one of the subsets. 
     
     
       11. A method comprising:
 generating a fast Fourier transform (FFT) of an engine knock signal generated by an engine knock sensor; 
 determining an engine knock intensity based on one of a maximum of and an average of the FFT; and 
 determining a status of the engine knock sensor based on the engine knock intensity, a plurality of predetermined knock intensity thresholds, and a rotational speed of an engine crankshaft. 
 
     
     
       12. The method of  claim 11 , wherein the predetermined knock intensity thresholds are based on the rotational speed of the engine crankshaft. 
     
     
       13. The method of  claim 12 , wherein the plurality of predetermined knock intensity thresholds includes a plurality of low intensity thresholds and a plurality of high intensity thresholds. 
     
     
       14. The method of  claim 13 , further comprising:
 setting the status of the engine knock sensor to failure when the engine knock intensity is between one of the low intensity thresholds and one of the high intensity thresholds. 
 
     
     
       15. The method of  claim 14 , further comprising:
 incrementing a failure count when the status of the engine knock sensor is set to failure during a predetermined time interval. 
 
     
     
       16. The method of  claim 15 , further comprising:
 outputting the failure count after the predetermined time interval; and 
 resetting the failure count to zero after the predetermined time interval. 
 
     
     
       17. The method of  claim 16 , further comprising:
 actuating one or more of a plurality of fuel injectors and a plurality of spark plugs based on the engine knock signal when the failure count is less than or equal to a predetermined failure count threshold. 
 
     
     
       18. The method of  claim 11 , wherein the FFT includes a plurality of subsets corresponding to a plurality of frequency ranges. 
     
     
       19. The method of  claim 18 , wherein each of the subsets includes a plurality of intensities corresponding to a plurality of frequencies. 
     
     
       20. The method of  claim 19 , further comprising:
 determining the engine knock intensity based on one of a maximum of and an average of intensities corresponding to one of the subsets.